Sinn Féin Leader Held in Connection With Killing of Woman IRA Thought Spied for British Military

Anger grew on the republican side of the political divide in Northern Ireland on Saturday as Sinn Féin President Gerry Adams spent a third day under arrest in connection with one of most notorious unsolved killings attributed to the Irish Republican Army during the bloody era known as the Troubles.

Mr. Adams, 65, a key figure in the Irish republican movement, was arrested after he voluntarily presented himself at Antrim police station on Wednesday evening. He has repeatedly denied any role in the 1972 killing of Jean...